Uric acid is the product of human purine metabolism. Generally, the human serum uric acid level is 200-410 μmol/L, with female usually lower than male. Elevated levels of human uric acid are usually associated with abnormal purine metabolism or abnormal renal excretion, and internationally the concentration of male serum uric acid above 420 μmol/L or female's above 357 μmol/L is defined as hyperuricemia. And hyperuricemia often causes gout. Gout was defined by the Egyptians in the year 2640 BC and was recorded in Hippocrates' medical work in 400 BC. Today, due to changes in diet and lifestyle, the number of hyperuricemia and gout patients increases, and hyperuricemia and gout have become a common rheumatic disease in the modern society.
People are rarely concerned about their own serum uric acid levels and often take no treatments until the gout symptoms appear. At present, the main treatments include anti-inflammatory and analgesic which are operated by medicines such as colchicine and non-steroidal anti-inflammatory medicines, and continuous medication for 1 to 2 weeks can significantly suppress the gout symptoms. Indomethacin can also treat acute gout, and injection of the adrenocorticotropic hormone has a better, more rapid curative effect. Allopurinol, having a clear target of action, is the only commercially available drug for reducing the uric acid production and the serum uric acid level by inhibiting the xanthine oxidase activity, but it has a slow effect and may aggravate the gout symptoms in the initial use. However, the anti-inflammatory, analgesic medicines and the allopurinol with a clear action mechanism have some toxicity and side effects during treatment, and therefore patients who have been suffering from chalkstone are mostly subjected to surgery for removing the chalkstone and correcting the joints. In the treatment of asymptomatic hyperuricemia, doctors recommend adjusting the diet or orally taking some food-borne medicines, so as to achieve the purpose of slowly decreasing the level of serum uric acid.
Protein is an essential nutrient in our daily life and contains a lot of bioactive substances—bioactive peptides, which may have antihypertensive, cholesterol-decreasing, antithrombotic, anticancer, and anti-oxidation activities and other biological activities. However, these bioactive sequences are present within these protein substrates, and when the protein enters the human stomach and intestinal tract while being eaten, these bioactive peptides cannot be released completely by enzymes in the stomach and intestinal tract. The modern biological enzymolysis technology, as a method for efficiently releasing the bioactive peptides inside the protein, is mainly to imitate the proteolytic process of the human body's digestive system. It could efficiently obtain the bioactive peptide with y specific biological activity by modification of hydrolysis conditions as well as type and concentration of the protease, since the hydrolyzation is in vitro reaction.
Besides, Maillard reaction, as a non-enzymatic browning reaction often occurring between reducing sugar and amino acids, peptides, proteins or any nitrogen-containing compounds in the process of food processing or storage, has a fast reaction process and complex internal composition changes and may even produce some substances with strong biological activity, it is widely reported that the Maillard reaction can significantly enhance the anti-oxidation activity of protein peptides, therefore it is also an effective methods of enhancing the biological activity of protein peptides.
Saury, as the middle- and upper-level ocean fish, has rich protein but a lower added value, and is mainly used as inexpensive food or feed. At present, several studies have been reported on the preparation of antioxidant peptides by biological enzymolysis, but there are still lack of studies of using saury to prepare antihyperuricemic components. If saury is used as raw materials to produce protein peptide products that significantly reduce uric acid levels of human, not only the application of saury is expanded and its economic value is improved, but more importantly people's quality of life can be improved, thus having great social significance.